(NaturalNews) Lymphoma patients with vitamin D deficiency are twice as likely to die from their cancer than patients with sufficient blood levels of the vitamin, according to a study conducted by researchers from the Mayo Clinic and presented at a meeting of the American Society of Hematology.

Researchers took blood samples from 374 patients between 2002 and 2008 who had been recently diagnosed with a cancer of the white blood cells known as diffuse large B-cell lymphoma. The average participant age was 62.

Approximately 40 percent of all lymphomas are of the diffuse large-B cell type. The disease mainly affects people over the age of 50.

The researchers found that roughly 50 percent of all participants suffered from vitamin D deficiency at the beginning of the study, defined as having blood levels below 25 nanograms per liter. Over an average of three years of follow-up, patients with vitamin D deficiency were 50 percent more likely to have their cancer worsen and twice as likely to die as patients with vitamin levels above 25 nanograms per liter.

Researchers have known for a long time that vitamin D helps regulate calcium absorption and thus plays a crucial role in bone and dental health. Recent research suggests that the vitamin may also help regulate the immune system, and that higher levels can help prevent against chronic diseases such as Alzheimer's, cancer, diabetes and dementia. Some researchers are making the case that for these benefits, vitamin D levels must be maintained at a level closer to 40 nanograms per liter.

The Mayo Clinic researchers used the 25 nanogram per liter cutoff because that is the level at which the body begins to leach calcium from its own bones, and is therefore a well-defined deficiency threshold.

Prior research has suggested that vitamin D deficiency may worsen the prognosis for patients with breast, colon and throat cancers.